Aerodynamic coupling for jet noise suppressors



y 1965 J. A. MORGAN ETAL 3,

AERODYNAMIC COUPLING FOR JET NOISE SUPPRESSORS Filed Feb. 23, 1962 2 Sheets-Sheet 1 FIG-I INVENTOR; JAMES A. MORGAN F'REDERIC M. ORAN ATTORNEYS y 1965 J. A. MORGAN ETAL 3,

AERODYNAMIC COUPLING FOR JET NOISE SUPPRESSORS Filed Feb. 23, 1962 2 Sheets-Sheet 2 United States Patent ice 3,195,678 AERODYNAMI'C COUPLING FGR JET NGISE SUPPRESSORS James A. Morgan, .Wycoif, N..I., and Frederic M. Oran,

Riverdale, N.Y., assignors to Industrial Acoustics Company, Inc, New York, NY.

Filed Feb. 23, 1962, Ser. No. 175,001 20 Claims. (Cl. 181-33) This invention relates to a coupling and more particularly to means for coupling a noise suppressor to a jet stream.

The discharge of high velocity gases into a relatively static gaseous medium produces a turbulence which generates a broad spectrum of noise. The spectral characteristics thereof depend in part on the diameter of the jet orifice or nozzle; for typical values encountered in aircraft jet engine operation, this noise has component frequencies above, throughout and below the audible range.

In treating this noise problem it has been proposed to modify the noise spectrum by effectively changing the jet diameter whereby the normally audible noise is translated to the ultra-audible range. Devices of this character, referred to as diffuser-type suppressors, comprise in essence a perforated diffusion receptacle, known in the art as a colander. The perforations therein act .to convert the large-diameter jet issuing from the engine exhaust nozzle, into a plurality of small-diameter jets issuing from the colander perforations. By virtue of this arrangement the effective noise spectrum is said to be confined largely to the ultra-audible range where it is considerably less bothersome.

To obtain satisfactory performance with the colander type suppressor, it has been found necessary to accurately match the colander to the jet exhaust nozzle. This matching involves a careful correlation between the diameter of the engine nozzle and the diameter of the colander together with a proper spacing between the nozzle and the colander entrance so that a close coupling is realized. Experience and analysis have demonstrated that failure to provide a proper match produces a substantial deterioration in the performance of the suppressor. To avoid this it has been the practice heretofore to provide a specific colander configuration for a specific engine configuration. In effect, each colander must be tailor-made to a specific type engine. Thus it has been the custom heretofore to provide a particular colander for the J-57 jet engine and a different colander for the larger diameter 1-75 engine; these colanders are not interchangeable.

In view of the many engine configurations presently operational and in view of the constantly changing engine types, it may be seen that maximum utilization of a single colander is not realized. Moreover, obsolescence of a particular type jet engine produces a corresponding obsolescence of the associated suppressor.

In addition to degradation in acoustic performance, mismatch also engenders other problems. In the case of an oversized colander, back-flow is created. This back-flow causes a temperature rise which complicates engine calibration and check-out and may even damage engine accessories such as components of the aircraft hydraulic system. During after-burner operation, mismatch resulting from the use of an oversized colander causes a violent back pulse or sonic boom to be generated which produces substantial shock to nearby structures.

Aside from the problem of mismatch, present colander type suppressors have limited use. During after-burner operation exhaust temperatures rise about 2000 F. and reach the neighborhood of 3000 F. This temperature has been suiiiciently high to cause fairly rapid structural deterioration of the colander. (Components thereof start to melt after about ten to fifteen seconds of after-burner 3,195,678 Patented July 20, 1965 operation.) It has accordingly been the practice heretofore to employ the colander only during the so-called military operation of the engine, that is without afterburner operation. This limitation has persisted notwithstanding attempted uses of a liquid coolant; the severe thermal shocks generated by application of the coolant produce rapid suppressor deterioration.

It is accordingly one object of the invention to provide means for coupling any one of a plurality of varying-diameter jet exhausts to a single universally sized diffuser-type suppressor, thereby providing proper matching between the suppressor and exhaust to preserve acoustic performance and aerodynamic compatibility.

A still further object of the invention is to provide such a coupling means which enables suppressor operation in the after-burner mode of engine operation.

A still further object of the invention is to provide diffuser means for efficiently diffusing a gas stream.

An additional object of the invention is to provide means coupling a diffuser-type suppressor to a jet exhaust whereby the aerodynamic and acoustic features of the colander are improved.

Another object of the invention is to provide means for coupling a suppressor to a high temperature jet stream for permitting suppressor use during high temperature operation and wherein the suppressor operates at a lower temperature thus permitting a reduction in the fabrica tion costs thereof.

Additional objects of the invention are to provide im proved aerodynamic coupling and matching means useful in the treatment and control of high velocity streams, an improved stream diffuser and improved high temperature stream cooling means.

A still further object of the invention is to provide improvements in diffuser-type suppressors.

These and other objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements and combinations herein shown and de scribed.

Serving to illustrate exemplary embodiments of the invention are the drawings of which:

FIGURE 1 is an elevational view partly in section of a colander-type suppressor and a coupling unit according to the invention for coupling the suppressor to a jet exhaust; the coupling is illustrated in a position angularly displaced 45 about its axis from its normal position;

FIGURE 2 is in part an elevational view of the entrance to the suppressor and in part a section-a1 view taken along the lines 2-2 of FIGURE 1;

FIGURE 3 is a front and FIGURE 4 is a side elevational view of a coupling unit according to the invention;

FIGURE 4A is an elevational view illustrating a modification of the coolant distribution system.

As seen in FIGURES 1 and 2, a colander suppressor according to the invention comprises a perforated member 10 of generally cylindrical shape coaxially disposed within a semi-cylindrical base section 11 of a shroud 12. A tapered entrance 13 is provided at one end of the shroud while the exit section 14 thereof comprises a vertical duct smoothly developed from the diametricallyopposing sides of base 11.

Colander 10 includes a perforated conical cap 15 at the far end thereof, the apex of which abuts the shroud and the base of which is disposed partially within the colander with clearance therebetween. The cap 15 is secured as by welding to three axially directed mount- .5 ing plates 16 disposed around the periphery of the cap and these are secured in turn as by bolting to respective flanges 17 secured to the shroud.

The opposite or entrance end of colander lltl, which includes an imperforate neck 13 is provided with a flange 19 which is secured as by bolting to a flange 24 on shroud entrance 13.

For coupling the suppressor to a jet exhaust issuing from a tail pipe 22 such as indicated by the arrow, coupling means are provided which include a diffuser generally indicated at 3i). A coolant system comprising coolant supply means, generally indicated at 49, and a coolant spray system generally indicated at d, are integrated with the diffuser in such a manner that the coupling, diffusion and cooling function are implemented in a common structure. For a fuller understanding of the coupling reference may be had to FIGURES 3, 4.

As seen in FIGURES 3 and 4 the coupling includes a coaxially disposed exhaust diffusion member 31 the sides 32 of which are conical and the face of which comprises a convex surface 33. port 31b and also includes a coaxial hollow tube 34 which is partially enclosed by member 31 and in part extends out of the rear of diffuser 31 in the direction of the exhaust stream. For certain modes of operation, the distal end of tube 34 is fitted with a perforated cap 3401. For other modes (see FIG. 4A), an inlet pipe 8th is slidably inserted in tube 34 and caps 31 are welded to the upstream end of pipes 43 which are described more fully hereinafter.

The above assembly is arranged for disposition in or near the center of the exhaust stream which is symbolically indicated by the arrow. Member 311 is oriented in such a manner that convex face 33 faces upstream and receives the impact of the jet exhaust. This orientation and positioning is accomplished in part by four hollow struts 35 which are spaced around the periphery of the coupling unit, the spacing preferably being equal between all struts.

One end 35a of each strut 35 includes a 90 elbow and this end is inserted into a respective opening in the side 32 of member 31. A concentric sleeve 36 is provided for each strut end, these sleeves being secured to the wall 32 and adapted, in combination with a pivot pin 37 which passes through holes in sleeves 36 and strut 35, to provide articulation of member 31 so that the same is pivotally mounted with respect to each of the struts 35. It may 'be seen from the above that the junction of member 31 This feature colander 10. There is accordingly provided for each strut a connector 38 fixed as by bolting to the colander neck 18 and having a pair of flanges 38a. The flanges receive cylindrical retainer plugs 39 which are rotatably installed in the flanges and are fixed as by welding to the respective strut 35. The end of each strut 35, thus pivotally coupled to colander 10, is flush fitted to a pipe 43 and the opposite end thereof is telescoped within and secured as by welding to a larger diameter pipe 44. The latter is telescoped with clearance between a tubular section 44a and an elbowed fitting 44b. The latter two are fixed in spaced relation by a separating ring 440. Pipe 44b communicates with the coolant supply system as generally described in connection with FIGURES 1 and 2 and more fully described hereinafter; the labyrinth just described provides both articulation and leakage.

Connected to each strut 35 and in communication with Member 31 is provided with a relief periphery of manifold ifications will occur to those skilled in the art.

pressor. The upstream end of the conduits 61 and 62 are turned inwardly and .seeured to respective openings in strut 35 while the oppositeends thereof connect to respective hollow spray rings 66 and 67. Ring 66 is of larger diameter than ring 6'7; the latter is located downstream of member 31 while ring 66 generally circumscribes member 31. The rings 66 and 67 each include suitable spray orifices which are disposed along the circumference of each ring so as to direct the spray in the directions indicated in FIGURE 4. This spray orientation is preferably adjusted to effect a substantially uniform temperature gradient longitudinally along the col ander wall so as to reduce warpage.

In addition to serving as a support for thedilfuser member and as a support and conduit for the spray rings, the struts 35 appear to perform a beneficial aerodynamic function. Shock wave fronts generated by member 31 are apparently dissipated by the struts thus minimizing structural loads on other components.

The above-described arrangement provides eflicient coupling between the colander Ill? and jet exhaust pipe notwithstanding variations in the diameter of the latter. Acoustic performance is improved over that available with an imperfectly matched colander alone. The organization and articulation of the elements enables the system to continuously withstand the severe thermal conditions and shocks characteristic of jet exhaust environments.

v For supplying coolant to the coupling an intake section may be employed such as illustrated in FIGURES l and 2. There is accordingly provided an inlet pipe id which is coupled to a ring manifold "I'll secured to flange l? of colander Ml. Distributor pipes '72 spaced around the i, connect with the respective pipes 4 which communicate in turn with the struts 3 5. Coolant is thereby supplied to the struts, spray rings as, 6)" and diffuser member. As in the case of the coupling between pipes and 4%, sufficient clearance is provided in the region where each strut 35' enters member Sll ,so as to insure suflicient leakage for additional cooling.

In the liquid cooling mode, water or other suitable coolant is fed to manifold 71 and thence to distributors '72, pipes 4 th, t? and struts 35. From thelatter, the coolant feeds to spray rings 66, d7 an-d'ditfuser 31 where terminal discharge occurs.

In an alternate coolant feed arrangement (see FIG. 4A), a coaxially disposed inlet pipe 8% is connected to the pipe 34- to supply the liquid discharge points by flow up struts 35 to rings 66, 67 and to points of leakage in the system. in either case the diffuser functions as a component of the cooling system, either as a feed point or as one of the discharge points.

The cooling function is sufficiently effective to permit the use of materials in the colander identical with those heretofore suitable only for military operation and the amount of coolant required during afterburner operation is less than that which has been required in previous, usually much larger suppressor systems.

Although enormous thermal shocks are generated water temperature may be in the order of 33 F. and exhaust temperature in the range 2000 to 3060" F.the articulation and general organization of the components provides long and reliable service.

In practising the invention other applications and mod- The invention is accordingly not limited to the specific mechanics shown and described; departures may be made therefrom within the scope of the accompanying claims without sacrificing its chief advantages.

What is claimed is:

l. oupling means for adapting a jet exhaust sound suppressor to variable diameter jet exhausts comprising a plurality of supports each movably coupled at one end to said suppressor, and a diffuser structure movably coupled to the other end of each support so as to be located substantially within said exhaust and .to receive the impact thereof, said movably coupled ends of said supports being located in a region protected by said diifuser structure.

2. A coupling as defined in claim 1 in which said diffuser structure is rotatably coupled to said support ends and said rotatably coupled ends are located within said diffuser structure.

3. A coupling as defined in claim 1 in which said supports comprise struts extending inwardly and downstream from the entrance to said suppressor.

4. A coupling as defined in claim 1 in which said diffuser includes a convex face and the sides thereof are generally conical.

5. Coupling means for adapting a jet exhaust sound suppressor to variable diameter jet exhausts comprising a plurality of supports each rotatably mounted at one end to said suppressor, a diifuser structure rotatably coupled to the other end of each support so as to be located substantially within said exhaust and to receive the impact thereof, said rotatably coupled ends of said supports being located within said diiiuser structure so as to be protected thereby.

6. Coupling means as defined in claim 5 in which said diffuser structure comprises a generally conical member having a convex face which receives said impact.

7. Coupling means as defined in claim 5 in which said supports comprise struts.

8. Coupling means for adapting a jet exhaust sound suppressor to variable diameter high temperature jet exhausts comprising a plurality of supports each coupled at one end to said suppressor, and adapted to conduct a coolant, a diffuser structure movably coupled to the other end of each support so as to be located substantially within said exhaust and to receive the impact thereof, said movably coupled ends of said supports being located in a region protected by said diffuser structure, coolant discharge means in communication with said supports and means in communication with said supports for supplying coolant to said discharge means via said supports.

9. Coupling means as defined in claim 8 in which said diffuser structure includes additional coolant discharge means fed from said supports.

10. Coupling means as defined in claim 8 in which said supports are movably coupled at said one end to said suppressor.

11. Coupling means as defined in claim 8 in which said diffuser structure comprises a member having a convex face which receives said exhaust impact.

12. Coupling means as defined in claim 8 in which said region comprises the interior of said diffuser structure.

13. Coupling means as defined in claim 8 in which said discharge means comprise a hollow perforated tube downstream of said supports.

14. Coupling means for adapting a jet exhaust sound suppressor to variable diameter jet exhausts comprising a plurality of hollow supports each movably coupled at 6 one end to the entrance of said suppressor and adapted to conduct a coolant, a diffuser structure rotatably coupled to the other end of each support so as to be located substantially within said exhaust and to receive the impact thereof, said rotatably coupled ends of said supports being located within said diffuser structure, coolant dis charge means in iiuid communication with said supports and means in communication with said supports for supplying coolant to said discharge means via said supports.

15. Coupling means as defined in claim 14 in which said supports comprise struts extending inwardly and downstream from the entrance to said suppressor and said discharge means comprise hollow rings having fluid discharge apertures.

16. Coupling means as defined in claim 15 in which said supply means comprise a manifold for receiving said coolant and distributing same to said struts.

1'7. Stream cooling and diffusing means for cooling and diffusing high velocity high temperature streams travelling in a conduit comprising a diffuser member located in the central region of said stream and having coolant discharge means and a blunt faced portion for receiving the impact of said stream, means connected to said conduit for movably connecting said difiuser member to said conduit and for transporting a liquid coolant and second coolant discharge means communicating with said stream and said connecting and transporting means.

125. Cooling and ditlusing means as defined in claim 17 in which said second coolant means comprise perforated rings disposed in coaxial relationship with said diffuser member.

19. Cooling and difiusing means as defined in claim 17 in which said connecting and transporting means comprise hollow struts which are pivotally joined to said diffuser member in the interior thereof.

20. Coupling means for eficiently matching aerodynamically a first relatively small diameter, upstream section of a high velocity stream system to a second larger diameter, downstream section of said system comprising a blunt faced diffuser member supported by struts movably attached to one of said sections and located in the stream-receiving entrance of said second section so as to receive the impact of said stream.

References Cited by the Examiner UNITED STATES PATENTS 2,325,905 8/43 Caulfield 18156 2,926,744 3/60 Towle et al. 18l-33 2,956,637 10/60 Lemmerman 181-33 2,971,599 2/61 Tobias 181-53 FOREIGN PATENTS 791,112 2/58 Great Britain. 831,776 3/60 Great Britain.

LEO SMILOW, Primary Examiner.

C. W, ROBINSON, LEYLAND M. MARTIN,

Examiners. 

1. COUPLING MEANS FOR ADAPTING A JET EXHAUST SOUND SUPPRESSOR TO VARIABLE DIAMETER JET EXHAUSTS COMPRISING A PLURALITY OF SUPPORTS EACH MOVABLY COUPLED AT ONE END TO SAID SUPPRESOR, AND A DIFFUSER STRUCTURE MOVABLY COUPLED TO THE OTHER END OF EACH SUPPORT SO AS TO BE LOCATED SUBSTANTIALLY WITHIN SAID EXHAUST AND TO RECEIVE THE IM- 